Zoku Gekka Bijin ~Ouka no Koro~

After learning that his foster parents have been murdered, our hero returns to his hometown, where he once swore never to return again.
Here, he runs into his stepsister "Misao." They once promised themselves to each other. However, a detestable war separated them, and now Misao has her own family.
Our hero is asked to search into his deceased parents' inheritance and the mystery of history unfolds...

[From Gamelex]